The present invention relates to the field of therapeutic technology for healing biological tissue with electricity. More particularly, the present invention relates to an improved electrotherapy system for applying electrical microcurrents to biological tissue such as a person's body.
Electricity promotes healing of biological tissue damage and provides an anesthetic to pain. This result is believed to be related to the properties and characteristics of biological cells. Biological cells contain a bioelectrical potential across the stable cell membrane. The cells can be stimulated by a nerve signal or external stimulus which disrupts the ionic balance in the cell. Additionally, the polarity of a cell can be reversed in different states of rest or activity. One form of biological cell damage hinders the cell ability to return to an equilibrium condition. Electrical treatments are believed to stimulate biological cells to emulate or to regain normal cell function.
Electrical treatments have been attempted to treat arthritis, biological tissue damage, nerve damage, calcification and other ailments. Prior art devices have utilized different frequencies, pulse rates, amplitudes, and magnetic fields in the search for therapeutic and anesthetic treatments. Although alternating current electrical fields have been applied to tissue, alternating currents can cause undesirable electrolysis at the contact point between an electrode and the tissue.
Square waveform electrical currents are known to be effective for promoting healing and curative effects. Consequently, efforts have been made to create square waveforms for application to biological tissue. However, such efforts have not produced a satisfactory device for generating pure waveforms at high voltage. Representative examples of prior art devices, including devices having positive and negative electrodes attached to a person's body, are described in the following references.
In U.S. Pat. No. 4,554,923 to Batters (1985), an electrically conductive glove was placed on a person's hand. Electric current was passed through the glove and hand to reduce pain and edema in the person's joints. The glove permitted an electrode to be stationary relative to the hand and facilitated electrical contact between the glove and hand without an external conductive medium.
In U.S. Pat. No. 4,509,521 to Barry (1985), headache pain was treated by applying an electrode to a person's neck or head, and by attaching a single ground electrode to a distal portion of the person's body. Electrical pulses from the electrode were applied between 60 and 150 volts and with a pulse width between 35 and 45 microseconds. The patent opined that each pulse should have the characteristics of a square waveform, and that other waveform shapes were not successful in providing relief. However, the disclosed device utilized a 20 turn primary and a 200 turn secondary transformer for altering the input to output voltage after the waveform was created. This device has inherent limitations because internal resistances in the transformer break down the waveform quality and prevent the formation of a square waveform.
U.S. Pat. No. 4,233,965 to Fairbanks (1980) described a device having two electrodes and a magnet for transmitting electricity through a person's body. One of the electrodes cooperated with a concentric electromagnet to produce a magnetic field for driving current into the tissue and toward a second electrode near the person's head. Rectangular or square wave positive polarity pulses were applied through a first electrode, and electrolysis at the tissue-electrode interface was minimized by the spreading effects of the magnetic field. Low voltage treatments between 20 and 27 volts DC at up to 400 microamps were applied continuously for up to eight hours.
U.S. Pat. No. 3,946,745 to Hsiang-Lai et al. (1976) described a device for generating an electrical signal comprising successive pulse pairs of opposite polarity, referred to as biopulses. Each biopulse included a fore-pulse and an aft-pulse having a reverse polarity. An electrode was attached to the tissue, and a signal pulse generator included a transformer for increasing the biopulse voltage. The output transformer generated an irregular waveform transmitted directly to the electrode load. To reduce the distortion of the output, a pair of resistors connected in parallel were substituted for the transformer so that open circuiting of a resistor would flow current through the other resistor. However, the patent disclosure anticipated that open circuiting of both resistors was possible, and that a potentially dangerous hazard might exist.
These electrical devices demonstrate the difficulty of generating a high voltage square waveform for application to biological tissue. Although transformers have been positioned between low voltage circuits and electrodes to step up the voltage after the waveform is generated, such waveforms are significantly distorted. High quality transformers reduce the amount of waveform distortion but are expensive and do not efficiently produce the desired microcurrent treatment. A need, therefore, exists for an improved system for providing electrical stimulation to a person's body.